Mounting for diaphragms of sound boxes



Jan. 21, 1930. EDlSON 1,744,533

MOUNTING FOR DIAPHRAGMS OF SOUND BOXES Filed April 30; 1925 INVENTOR, TM Q. CM

-Z Am TTORNEY Patented Jan. 21, 1930 UNITED STATES PATENT FFME THOMAS A.EDISON, OF LLEWELLYN PARK, VIEST ORANGE, NEW JERSEY, ASSIGNOR TO THOMASA. EDISON, INCORPORATED, 013 'WEST ORANGE, NEW JERSEY, A COR- PORATIONOF NEW JERSEY MOUNTING FOR DIAPHRAGMS OF SOUND BOXES Application filedApril 30, 1925.

My invention relates to mountings for the diaphragms of sound boxes andwhile particularly designed for use in phonographic sound boxes, myinvention is also applicable to other types of sound boxes, such, for example, as telephone transmitters and receivers.

In order to obtain the best acoustic results, it is essential in thecase of a sound box employing a vibratory diaphragm to mountthediaphragm resiliently in the sound box in order that the same mayproperly vibrate and function. For this purpose it has heretofore beencustomary to clamp the diaphragm of asound box in position in the latterbetween gaskets formed of soft rubber. Rubber, however, deterioratesquite rapidly and where gaskets of this material are employed, suchgaskets, in a comparatively short time, lose their elasticity and becomehard and brittle. This is due, principally, to the presence of sulphurin the rubber and the fact that sulphur is subject to oxidation. WVhenthe rubber gaskets of a diaphragm mounting of a sound box have thusdeteriorated, the diaphragm is apt to be loose in its mounting and thefunctioning thereof will be imp aired. In the case of av phonographreproducer, for example, such deterioration is likely to result inrattling, blasting and other imperfections in the reproduction.Moreover, the easings of phonograph reproducers are generally given anattractive finish by plating the same with gold or nickel, and becauseof the presence of the sulphur in the rubber gaskets, this finishfrequently becomes badly tarnished.

The principle object of my invention is to provide an improved mountingfor sound box diaphragms whereby the foregoing objections and defectswill be obviated, and wherein the mounting will retain the desiredresiliency for an indefinite period.

I have found that the foregoing object may be attained by employing inmountings of the character described gaskets 0f subereous material orcork instead of the usual soft rubber gaskets. Cork is highly suitablefor this purpose for it is a substance which retalns its elasticityindefinitely, and which, no matter Serial No. 26,967.

how long it is used, is practically unaffected by changes in atmosphericor weather conditions. This is undoubtedly due to the fact that cork isweather exposed for years in the formation thereof, and has reached thestage where it is no longer subject to any appreciable changes by reasonof climatic conditions. While natural cork may be used for the gasketsof my improved mounting, it is extremely difiicult to obtain anyappreciable quantity of the same which is free from hard particles ofbark and openings or crevices. Moreover, different lots of natural corkvary appreciably in resiliency or elasticity. Accordingly, it ispractically impossible to produce gaskets of natural cork which will beof uniform resiliency and texture. I therefore preferably form thegaskets of the material known as composition cork. This material is madeby grinding natural cork, eliminating all hard particles, such as piecesof bark and foreign substances, therefrom, and then pressing the groundcork into coherent sheets or slabs under enormous pressure. It isapparent that the composition cork thus produced is free from glue andglue-like substances. hlioreover, this composition cork is of veryuniform elasticit or resiliency and texture and is graded in accordancewith the fineness of the ground cork from which it is formed. Ipreferably employ for the gaskets described, composition cork of a finegrade.

Further objects and features of my invention will be hereinafter morefully described and claimed.

In order that my invention may be more clearly understood, attention isdirected to the drawing accompanying and forming a partof thisspecification, and in which:

Figure 1 is a sectional view of a phono graph reproducer equipped with:1 diaphragm mounting in accordance with my invention; and

Fig. 2 is a plan view of one of the gaskets used in the diaphragmmounting of the reproducer shown in Fig. 1.

Referring to Fig. l of the drawing, the reproducer shown is of theEdison type and comprises the usual cup 1 having a sound chamber 2 whichis circular in cross-section.

The sound chamber 2 is provided with a seat for a diaphragm 3, saiddiaphragm being held against the seat at its edge portion between twoannular packing rings or gaskets, 4, 4 by means of a locking ring 5screwed into the ,cup. The gaskets 4t, 4t are made of subereous materialsuch as cork or composition cork,

- preferably the latter, as described above. A

thin smooth metal bearing or clamping ring 6 is disposed between thelower gasket 4 and the locking ring 5 to prevent deformation of thegasket upon turning movement of the locking ring when the latter istightened.

The reproducer cup 1 is provided with a rearward extension 7, and afloating weight 8 is pivotally connected to the extension 7 for movementabout a vertical axis by means comprising pivot blocks 9, 9. Thefloating weight 8 is supported from the pivot blocks 9, 9 by means of aflat spring 10, one end of which is secured between the blocks 9, 9 andthe other end of which is secured to the adjacent end of the floatingweight. A stylus lever 11 is pivoted intermediate its ends at 12 on thefloating weight 8, one end of this lever being provided with areproducing stylus 13, and the opposite end thereof being connected tothe center of the diaphragm 3 by means of a link 14. This link extendsthrough a suitable opening 15 provided in the floating weight 8. A pin16 secured to the forward end of the floating weight 8, extends within aloop 17 secured to the underside of the reproducer cup 1 and coacts withthis loop to limit the vertical and lat-, eral movements of the floatingweight with respect to the reproducer cup.

lVhile'I have specifically described a preferred form of my improveddiaphragm mounting, it is to be understood that the same is subject tovarious changes and modifications without departure from the spirit ofmy invention and the scope of the appended claims.

Having now described my invention, what I claim as new and desire toprotect by Letters Patent is as follows:

1. A coherent resilient gasket for a. diaphragm mounting of thecharacter described formed of composition cork which is of substantiallyuniform texture and resiliency and which is free from glue and gluelikesubstances, substantially as described.

2. A coherent resilient gasket for a diaphragm mounting of the characterdescribed formed of composition cork from the cork of which all bark andhard foreign substances have been eliminated and which is free from glueand glue-like substances, substantially as described.

This specification signed this 28th day of April, 1925;

THOS. A. EDISON.

